TITLE: GCN CIRCULAR NUMBER: 10633 SUBJECT: GRB 100418A: MASTER-Net optical observations DATE: 10/04/20 10:45:29 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, V.Lenok, O.Gres, O. Irkutsk State University V.Yurkov, Yu.Sergienko, D.Varda, A.Garusina Blagoveschensk Educational State University, Blagoveschensk E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zimnukhov, M. Kornilov Sternberg Astronomical Institute, Moscow State University A. Tlatov, A.V. Parkhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalozhnih, T.Kopytova, A.Popov Ural State University, Kourovka MASTER robotic telescope (MASTER-Net: http://observ.pereplet.ru, testing telescope) located at Tunka Valley (Baykal, Siberia) was responted to the GRB 100418A (Swift Bat alert, Marshall et al, GCN CIRC 10612) 21 sec after Notice time (~ 8 sec delay in internet socket) and 31 s after the GRB time ( Sun Alt -8 degrees) . There is now OT on the first 10-s exposition time unfiltered images inside Swift XRT error box (Pagani et al., GCN CIRC 10622) brighter 14.5. The message may be cited. mailto: lipunov@sai.msu.ru